Team #2:Kyle Lynch

David TeicherShu Xu

The Partial Oxidation of Propylene to Generate Acrolein

Project Objective Process Background Material Balance Simple Kinetics and Rate Expressions Pressure Drop and Reactor Configuration Multiple Reactions Energy Balance Optimization and Conclusions

Design a Fixed Bed Reactor (FBR) for the production of acrolein by the partial oxidation of propylene

Produce 75,000 metric tons acrolein per year

Optimize the reactor design to minimize cost

Literature Review ◦ Research information on raw materials and products◦ Investigate catalysts and reaction kinetics

Reactor Design◦ Develop mole balances for multiple reactions◦ Implement pressure drop & energy balance equations◦ Optimize reactor

Acrolein◦ Raw material used for the production of pyridine, β-picoline, and some essential amino acids1

◦ Used for cleaning irrigation ditches, and other derivatives can be made into rubbers, glues, and polymers2

◦ Anti-microbial behavior Biocide in oil well to suppress the growth of bacteria2

◦ 100-500 million pounds produced in the U.S. in 20022

CH2=CH-CHO

Industry produces acrolein by the partial oxidation of propylene using oxygen and steam

The reaction is carried out in a catalytic FBR ranging between 350-450 °C1

Gaseous products leave and are quenched by cold water, then enter absorption column for product recovery3

CH2=CH-CH3 + O2 CH2=CH-CHO + H2O

Design 1-Preliminary mass and energy balance

Design 2-Reactor volume using simple reaction rate expression

Design 3-Pressure drop and reactor configuration

Design 4-Multiple reactions

Design 5-Energy balance on multiple reactions

Final Design-Optimization

A total of two weeks each year are allotted for scheduled shutdowns

All reactants and products are vapors

Air is used as an oxygen source

A 1:11 ratio of propylene:oxygen is outside the flammability limits4

The inlet pressure is 1 atm5

Negligible kinetic and potential energy losses

Isothermal, T=623.15 K5

SpeciesFeed Rate to Reactor

(kgmol/s)Change in Reactor

(kgmol/s)Effluent Rate

(kgmol/s)

Propylene, C3H6 0.05190 -0.04412 0.00779

Oxygen, O2 0.57090 -0.04412 0.52679

Nitrogen, N2 2.14768 0 2.14768

Acrolein, C3H4O 0 0.04412 0.04412

Water, H2O (v) 0 0.04412 0.04412

Total 2.77048 0 2.77048

• Material balance for annual production rate of 75,000 metric tons

*Design specification for acrolein production rate is 0.04412 kmol/s

CH2=CH-CH3 + O2 CH2=CH-CHO + H2O

All Design 1 assumptions

A conversion of 0.85 will be achieved3

1000 kg/m3 is Catalyst bulk density6

Reactor is at steady state

Ideal gas law applies

Simple kinetics6

To simulate the FBR being designed, a Polymath® model was developed.

The Polymath® reactor was created as a function of catalyst weight

Aspen Plus® used to examine the relationships between temperature, reactor volume, and conversion

PP rW

F

2/1

2OPA CCkr

Developed an isothermal reactor model as function of catalyst weight using Polymath® and ASPEN ®

* Higher temperatures require smaller reactors for same conversion

V = 167,000 m3

All Design 2 assumptions – Inlet pressure is 3 atm6

Catalyst void fraction of 0.46

Particle diameter of 5 mm7

Inlet viscosity is that of pure steam4

Schedule 40 pipe used for multi-tube reactors8

Implemented Ergun pressure drop equation into design

Optimized reactor so pressure drop is less than 10%

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V = 8,643 m3

* Pressure drop decreases conversion

Reactions are carried out in a catalytic FBR with temperatures ranging between 350-390°C

Acrolein is desired product

Major by-products9

◦ Water◦ CO and CO2

◦ Acetadehyde

OHCOOHC 22263 335.4

OHCOOHC 2263 333

OHCOHC 42263 634

C3H6+ O2 C2H4O + H2O

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Symbol SpeciesChemical Formula

A Propylene C3H6

B Oxygen O2

C Acrolein C3H4O

D Water H2O

E Carbon Oxides COx

F Acetaldehyde C2H4O

G Nitrogen N2

HCarbon Dioxide

CO2

ICarbon

MonoxideCO

All Design 3 assumptions – 2830 kg/m3 is catalyst particle density10

Tan et al. reaction kinetics representative9

CO2 reaction rate independent of temperature

Modified the reactor to include multiple reactions Used approved reaction kinetics to calculate species flow

rates

V = 287.5 m3

Temperature (K)Acrolein OutletFlow (kmol/s)

Carbon Oxides and Acetaldehyde Total

Outlet Flow (kmol/s)Acrolein Selectivity

623 0.04412 0.05937 0.74

633 0.04949 0.05438 0.91

643 0.05401 0.04922 1.10

653 0.05760 0.04430 1.30

663 0.06032 0.03991 1.51

673 0.06227 0.03621 1.72

IHF

CFHIC FFF

FS

/

~

*Selectivity of acrolein increases with temperature

All Design 4 assumptions

227 W/m2-K is heat transfer coefficient6

Heat capacities are constant

Heats of reactions are constant

Coolant temperature is constant at 618.15 K6

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An energy balance across the reactor was introduced to further validate the model as a suitable representation of the actual reactor

Incorporated energy balance into reactor design Compared isothermal reactor and reactor with constant

coolant temperature

The Effect of Coolant Temperature on Temperature Profile

*Coolant temperature effects severity of hotspot

V = 281.3 m3

“Gain” measures the dynamic stability of the reactor

A “Gain”< 2 is desired

Coolant Temperature (K)Polymath® Model

Hotspot Temperature (K)Aspen Plus® Model

Hotspot Temperature (K)

658.15 674.12 674.11

659.15 675.24 675.24

GAIN 1.12 1.13

coolant

HS

T

TGain

The catalyst void fraction is 0.46

Catalyst bulk density is 1698 kg/m3 for α-Bi2Mo3O12 10

The inlet pressure is 3 atm6

The inlet temperature is 663.15 K9

The coolant temperature is constant at 658.15 K6

FEED

PRODUCT

B1

Specification Value

Feed Conditions

Temperature 663.15 K

Pressure 3 atm

Propylene:Oxygen Ratio 1:11

Propylene Conversion 85%

Catalyst

Bed Voidage 40%

Particle Diameter 5 mm

Bulk Density 1698 kg/m3

Bed Weight 185047.25 kg

Bed Volume 108.98 m3

Reactor

Length 2.40 m

Overall Reactor Diameter 7.60 m

Tube Diameter 0.0259 m

Number of Tubes 86,304

Heat Transfer Coefficient 227 W/m2-K

Coolant Temperature 658.15 K

Pressure Drop 9.54%

Species Annual Production (Metric Tons)

Propylene, C3H6 12,363

Oxygen, O2 613,288

Nitrogen, N2 2,269,470

Acrolein, C3H4O 75,008

Water, H2O 36,226

Acetaldehyde, C2H4O 6,783

Carbon Dioxide, CO2 25,779

Carbon Monoxide, CO 2,421

1John J. McKetta. “Acrolein and Derivatives” Encyclopedia of Chemical Processing and Design. 2Toxicological Profile for Acrolein, U.S. Department of Health and Human Service, Agency for Toxic

Substance and Disease Registry (August 2007). 3“Acrylic Acid and Derivatives.” Kirk-Othmer Encyclopedia of Chemical Technology. 4th Edition. 4Chemical Database Property Constants. DIPPR Database [Online]. Available from Rowan Hall 3rd

Floor Computer Lab. (Accessed on 1/26/08). 5L. D. Krenzke and G. W. Keulks, The Catalytic Oxidation of Propylene: VIII. An Investigation of the

Kinetics over Bi2Mo3O12, Bi2MoO6, and Bi3FeMo2O12. The Journal of Catalysis Volume 64 (1980) p. 295-302.

6Dr. Concetta LaMarca 7“Reaction Technology.” Kirk-Othmer Encyclopedia of Chemical Technology. 4th Edition. 8Perry, Robert. Perry's Chemical Engineers' Handbook. 7th. New York: McGraw-Hill, 1997. 9H.S. Tan, J. Downie, and D.W. Bacon, The Reaction Network for the Oxidation of Propylene Over a

Bismuth Molybdate Catalyst, The Canadian Journal of Chemical Engineering Volume 67 (1989) p. 412-417.

10Cerac Incorporated. “MSDS Search” 25 March 1994. Accessed: 8 April 2008. <http://asp.cerac.com/CatalogNet/default.aspx?p=msdsFile&msds=m000443.htm>